Synthesis, reaction and structure of a highly light-stable silver(i) cluster with an Ag4S4N4 core having a tridentate 4N-morpholyl 2-acetylpyridine thiosemicarbazoneligand: Use of water-soluble silver(i) carboxylates as a silver(i) source

Abstract

A novel neutral tetrameric silver(I) cluster [Ag(mtsc)]₄ was obtained from reactions of a tridentate ⁴N-morpholyl 2-acetylpyridine thiosemicarbazone ligand (N′-[1-(2-pyridyl)ethylidene] morpholine-4-carbothiohydrazide, Hmtsc) and silver(I) sources containing Ag–O bonds (Ag₂O, Ag(OAc), silver(I) 2-pyrrolidone-5-carboxylate _∞{[Ag(Hpyrrld)]₂}, silver(I) 5-oxo-2-tetrahydrofurancarboxylate _∞{[Ag(othf)]₂}, and silver(I) complexes with camphanic acid _∞{[Ag(ca)]} and _∞{[Ag(ca)(Hca)]}). The cluster was characterized by elemental analysis, TG/DTA, FTIR and single-crystal X-ray analysis in the solid state. The solution properties of the complexes were investigated using solution molecular weight measurement, ESI-MS and solution (¹H, ¹³C and ³¹P) NMR spectroscopy. The obtained cluster is a novel example of a light-stable Ag^I cluster with a tridentate thiosemicarbazone ligand and the second report of a crystal structure of a thiosemicarbazone silver(I) complex. The reaction of the tetramer with a large excess of PPh₃ gave dimeric complexes, namely, [Ag(µ(S)-mtsc)(PPh₃)]₂ and [(PPh₃)₂Ag(µ(S)-mtsc)₂Ag]. The chloroform solution of the tetrameric complex showed modest and effective activities against selected bacteria (Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa) and yeasts (Candida albicans and Saccharomyces cerevisiae), respectively, but it did not inhibit the growth of any selected microorganisms in a water-suspension system.